For better appearance and visibility, there is recently an increasing need for the technology for tailoring the surface of optical articles to be fingerprint proof or easy in stain removal. In particular, since eyeglass lenses, wearable terminals, and touch panel displays are readily fouled with stains like sebum, it is desired to form a water/oil repellent layer on their surface. In the state-of-the-art, there are available surface treating agents having antifouling, stain wipe-off, abrasion resistance and mar resistance. However, they are insufficient in chemical resistance, leaving the problem that their performance is degraded with fingerprints and detergents with the lapse of time.
Generally, fluorooxyalkylene-containing compounds exhibit, by virtue of their extremely low surface free energy, water/oil repellency, chemical resistance, lubricity, parting, antifouling and other properties. Taking advantage of these properties, they find use in a variety of industrial fields as water/oil repellent antifouling agents for paper and textiles, lubricants for magnetic recording media, oil-repellent agents for precision instruments, parting agents, cosmetic ingredients, protective films and the like. Inversely, the same properties indicate non-tackiness or non-adhesion to other substrates. Even if they can be coated to the substrate surface, it is difficult for the coating to tightly adhere thereto.
On the other hand, silane coupling agents are well known for their ability to bond surfaces of glass or fabric substrates to organic compounds. They are widely used as surface coating agents for numerous substrates. The silane coupling agent contains an organic functional group and a reactive silyl group (typically hydrolyzable silyl) in the molecule. In the presence of airborne moisture or the like, the hydrolyzable silyl groups undergo self-condensation reaction to form a coating. As the hydrolyzable silyl groups form chemical and physical bonds with the surface of glass or fabric, the coating becomes a tough coating having durability.
Patent Document 1 discloses a fluorooxyalkylene group-containing silane represented by the following formula.
Herein Rf is a divalent linear perfluorooxyalkylene group, R is C1-C4 alkyl or phenyl, X is a hydrolyzable group, n is an integer of 0 to 2, m is an integer of 1 to 5, and a is 2 or 3. When treated with this fluorooxyalkylene-containing silane, glass and antireflective film are improved in stain wipe-off. However, since both terminal groups are bonded to the substrate, surface lubricity is insufficient, and the coating is less satisfactory in sliding and mar resistance.